Modern production practice imposes quite a number of requirements upon machines for noncutting metal shaping, of which principal are as follows; further rise of productivity and quality of finished products accompanied by reduced power consumption and costs of attendance and maintenance.
The level of productivity of machines for noncutting metal shaping attained up to date, as far as it concerns the problems of automation and mechanization of charging the workpieces and discharge of the finished products, depends predominantly upon the traversing speed of the operative member, i.e., number of its working strokes per unit time which is restricted by a number of factors, of which cardinal ones are: load-carrying capacity of the crankshaft annular sliding-friction bearings, and the state of dynamic balancing of the system "working member--workpiece hand-led--machine frame" (drive inclusive).
Load-carrying capacity of the annular bearings is the function of the peripheral sliding speed (v) thereof and of the specific load (P) imposed thereon. The product of P and v may be assumed practically to be a constant value for the heretofore known materials from which bearings are made, within a certain lapse of time, since said product depends mostly upon the characteristics of the material of the sliding-friction bearing itself rather than upon the parameters of the machine, its particular design features and operation. The machine can be made more speedy due to an increased peripheral speed of the annular bearings, but it involves inevitably a corresponding reduce of the specific load on the bearings so that the problem remains eventually unsolved.
Notice should also be taken of the fact that in machines for noncutting metal shaping, such as radial squeezers, sliding-friction bearings of the crankshaft sustain nominal load exerted by the operative member when the latter produces pressure-shaping effect upon the work-piece being handled, said load being imposed at a certain angle of crankshaft turn called the working angle, with the result that much work of the drive is spent to overcome the forces of friction arising in the bearings. As the production output of the machine rises the amount of power consumed for overcoming the force of friction in the bearings increases so much that the amount of motor power consumed for the purpose gets commensurable with the power required for performing useful work, or even exceeds it by a factor of three or four, which is the case with such machines as radial squeezers. The result is abnormally high heating of the bearings which requires that the machine shall be provided, for attaining stable operation thereof, with automatic lubricant temperature control means, that use be made of special lubricant retaining its viscosity at elevated temperatures, an increased clearances in mating bearings be provided and that the entire system "operative member--workpiece hand-led--bed" be balanced and imparted the state of dynamic stability. As a result, all this complicates the machine, heightens power consumption and costs of attendance and in-service maintenance to such a great extent that application of said machines for accomplishing the functions they perform becomes economically unjustifiable.
Thus, to sum up all the afore-discussed, any increase in the productivity of the currently used crank presses and radial squeezers wherein a crank mechanism taking up nominal force applied for pressure-shaping of the workpiece being handled, is employed as a device for converting rotary motion of the drive into reciprocating motion of the operative member, is restricted by the load-carrying capacity of the crankshaft sliding-friction bearings and the amount of work due to friction arising therein.